thanks hetfield. i have exhausted the archives now and decided that it must be one of three things...1) serpentine belt, although in my case i doubt this. 2) feul injector pulse, but i doubt this as well...i would think that this noise is to faint to be heard outside the engine compartment. i can hear my noise from about 8 feet away with the hood closed. 3) lifter, seems like this would cause some sort of performance loss but i could be wrong. i guess i will have to experiment
i was hoping to find a definitive answer seeing as how so many duratec owners have experienced this